In prognathism except for teeth, jaw’s bones also participate in their entirety. When one of the jaws relies forward more than the other and the rest of the skull’s skeleton then we talk about prognathism.
Prognathism of lower jaw
When the lower teeth and/or the jaw relies forward as regards to the upper. This situation is usually associated with an extended chin affecting enough facial aesthetics.
Prognathism of upper jaw
When the upper jaw and the upper teeth relies forward as regards to the lower. In that case facial aesthetics is negatively affected whilst there is the risk fracture of the anterior teeth in an accident, particularly in boisterous young children.